Every website is different, so occasionally some of them may not work properly. As a workaround you can open the page in Safari, select the content, copy it, and paste it into Outread (select + and then Paste Text).
In case of content behind a paywall (e.g. NYT, WSJ) you should get best results when you open an article in Safari and then add it to Outread through the share extension. This way Outread will see the same content that you see (e.g. behind a paywall if you’re a WSJ subscriber).